High vacuum pump having vapor jet nozzles



April 8, 1941. u. LAMM HIGH VACUUM PUMP HAVING VAPOR JET NOZZLES Filed Jan. 18, 1959 Patented Apr. 8, 1941 HIGH VACUUM PUMP HAVING VAPOR JET N OZZLES Uno Lamm, Ludvika, Sweden, assignor to A11 manna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Application January 18, 1939, Serial No. 251,477 In Sweden January 22, 1938 8 Claims.

The present invention relates to a high vacuum pump of the so-called diffusion or vapor jet type having one or several series-connected pairs of co-axial nozzles, one nozzle in each pair projecting a vapor jet, generally of mercury vapor, into the other, said jet carrying off the gas molecules. When manufacturing such pumps from metal, it is known to combine each pair of such nozzles into a structural unit, in some cases to combine all the pairs of nozzles into one single structural unit capable of being removed as such out of the surrounding, in general substantially cylindrical casing. It is particularly important that the two cooperating nozzles of each pair are firmly secured to each other, so that the slot therebetween, after being once adjusted to the proper width, cannot be altered at the introduc tion into the casing nor later for instance by temperature variations. In enforcing this principle, another one has been to a certain extent neglected, namely, to obtain the smallest possible leakage of heat from the hot vapor to the casing of the pump. The present invention makes it possible to satisfy both of these principles in the same degree and consists in the first line in that one of the nozzles of such a pair supports the other by members arranged symmetrically around the common axis of the nozzles. By this symmetrical arrangement, any oblique stresses are avoided and it is therefore possible 1 to make the supporting members particularly thin so as to conduct the smallest possible heat quantity. Preferably the pairs of nozzles are also arranged coaxially with the casing, which also contributes in diminishing the heat leakage.

Three forms of the invention are illustrated in the accompanying drawing in Figs. 1-3, in which Fig. 1 shows an arrangement of two pairs of nozzles in longitudinal section, Fig. 2 shows another form of a single nozzle pair, and Fig. 3 a further form of a single nozzle pair-400th in longitudinal section.

Preferably all the nozzles are carried by a common vapor supply and distribution pipe so as to be removable from the casing together with this pipe. Fig. 1 shows such a pipe 6 carrying two pairs of nozzles. Said pipe is at the top connected to an external supply pipe [5 as well as to the upper discharging nozzle l by a screwed joint. The socket 4 of this joint has radial slots 5 through which part of the vapor is distributed to the nozzle. On the latter is screwed a sleeve 8 which by means of a thin extension 1 having a circular row of holes 9 is connected to the receiving nozzle 2.

The holes 9 form communicationsbetween the suction room of the pump and the nozzle slot and serve at the same time to reduce further the heat leakage through the thin cylindrical extension 1. By reason of the symmetrical shape and arrangement of the latter, the connection will still be sumciently rigid to maintain exactly the width of the slot between the nozzles adjusted in assembling the structure.

The receiving nozzle 2 has a downwardly divapor is condensed in the receiving nozzle, which contributes to the sucking action of the pump. Some flaps 20 at the lower end of the cylinder l0 may be bent inwards to center the nozzle 2 in the ring I6.

Thelower nozzle pair in Fig. 1 is arranged substantially in the same manner as that now described. As the vapor supply pipe ends at this nozzle, the arrangement is, however, somewhat simpler. The discharging nozzle simply forms the end of the vapor pipe, and a sleeve 3 is screwed on to it and is connected to the receiving nozzle [2 by a thin-walled portion I! having therein holes IS. The devices forming a. liquid seal are here quite analogous to those of the upper nozzle pair and are therefore designated in the same manner. They are only made with a smaller diameter for enabling the lower nozzle pair to be extracted through the hole in the upper ring l6.

Fig. 2 shows another form of a nozzle pair which as an example is devised for mounting on the end of the vapor pipe. The discharging nozzle 2| is here connected to the receiving one 22 by means of flanges 23, 24, respectively, between which several thin washers 25 can be introduced for an exact adjustment of their mutual position. Otherwise the connection is analogous to Fig. 1 with a thin-walled cylinder 21 having perforations 29.

In Fig. 3, the two nozzles 3|, 32 are connected with each other by bolts 33 symmetrically arranged in a circle, threaded into the receiving nozzle and provided with double nuts by means of which the relative position of the discharging nozzle may be adjusted. The liquid seal has here a form differing from Figs. 1 and 2, comprising a packing ring 34 of a suitable resilient material above which the mercury is collected. This form of the seal cannot, as those previously described, serve as a discharge for the condensed liquid, and such a discharge must therefore be provided in another manner, for instance by a separate port having a liquid seal.

I claim as my invention:

1. A high vacuum vapor jet pump made of metal and comprising a casing and at least one pair of cooperating nozzles therein coaxial with each other and with said casing, one of said nozzles delivering a vapor jet into the other, a downwardly projecting cylindrical extension on said latter nozzle, and a ring secured to said casing forming an annular groove embracing said cylindrical extension and forming a liquid seal therewith.

2. A high vacuum vapor jet pump made of metal and comprising a casing and at least two pairs of cooperating nozzles therein coaxial with each other and with said casing, one of the nozzles of each pair delivering a vapor jet into the other receiving nozzle, a downwardly projecting nozzles therein fed in parallel from a common i vapor supply pipe and operating in series so that one nozzle pair discharges into the partial vacuum created by the other, one nozzle of each pair discharging a vapor jet into the other, and each pair forming a structural unit coaxial with said casing, and a vapor supply pipe entering said casing from above and directly supporting said pairs of nozzles.

4. A high vacuum vapor jet pump made of metal and comprising a vapor supply pipe, a casing, a plurality .of vapor jet nozzle pairs in said casing operating in series ,so that one nozzle pair discharges into the partial vacuum created by another, at least one of the nozzle pairs consisting of one delivering nozzle secured to the said vaby means of members symmetrically arranged around the common axis of the nozzles.

5. A high vacuum vapor jet pump made of metal and comprising a vapor supply pipe, a casing, a plurality of vapor jet nozzle pairs inside said casing, of substantially smaller diameter than said casing and coaxial therewith, said nozzle pairs being fed in parallel from a common vapor supply pipe and operating in series so that one nozzle pair discharges into the partial vacuum created by the other, each nozzle pair consisting of one delivering nozzle secured to the common vapor supply pipe and one receiving nozzle coaxial therewith, one of said nozzles directly supporting the other nozzle of the pair by means of members symmetrically arranged around the common axis of the nozzles and the casing.

6. A high vacuum jet pump made of metal and comprising a casing, a plurality of vapor jet nozzle pairs of substantially smaller diameter than said casing arranged therein to be fed in parallel from a common vapor supply pipe and to operate in series so that one nozzle pair discharges into the partial vacuum created behind another, each nozzle pair consisting of one delivering nozzle and one receiving nozzle coaxial therewith, the latter nozzle having a substantially cylindrical, thin and perforated extension into which the delivering nozzle of the same pair is secured.

'7. A high vacuum jet pump comprising a casing, a vapor supply pipe, a plurality of pairs of vapor jet nozzles, the said pipe and nozzles being disposed centrally within the casing in spaced relation to the internal surface thereof, at least one separating and sealing ring member Within the casing whereby the nozzle pairs operate in series, with one nozzle pair discharging into the partial vacuum created by another pair, and rigid connecting means between the nozzles of each pair.

8. A high vacuum jet pump comprising a casing, a vapor supply pipe therein, a plurality of pairs of nozzles, each pair consisting of a high temperature delivery nozzle and a low temperature receiving nozzle, sealing means in the casing separating each pair from the adjacent pair whereby said pairs operate in series, and means for rigidly connecting the nozzles with said pipe, the means for such rigid connection of the receiving nozzles having cross-sections of such dimensions as to reduce to a minimum heat transfer from the delivery nozzles to the receiving nozzles.

UNO LAMM. 

